In a number of radar applications, features of interest in radar returns remain static for more than a single transmit and receive cycle. One such application is airborne ground mapping radar. One important metric in such applications is range resolution. Range resolution and cross-range resolution together determine the smallest sized ground objects or features that can be resolved by the radar. Range resolution in radar is proportional to signal (pulse) bandwidth, i.e. greater bandwidth allows better resolution. Generally, however, increasing pulse bandwidth requires greater equipment expense to effect the generation, transmission, reception, and resolution of increased pulse bandwidths.
Most conventional radar systems operate in a relative narrow frequency band; they use harmonic (sinusoidal) signals as carrier oscillations to transmit the information. The reason for that is rather simple; a sinusoid is an eigenoscillation of LC-contour, which is the simplest and, so, the most widely-used electrical oscillation system. The resonance features of such a system make possible frequency selection of the large number of information channels operating in the common environment (space, guiding, and optical communication lines).
However, it is a frequency band that determines the information content of radar systems, as the volume of information transmitted per time unit is directly proportional to a frequency band. To raise the information capability of a radar system, the widening of its frequency band is needed. The only alternative approach is an increase in information transmission time.
One inherent expense in widening a bandwidth for a radar application is that antennae for the system must be designed to achieve an optimal waveform for a particular bandwidth, i.e. to control the selection of range resolution over side lobe-levels, to determine Doppler tolerance and resolution, etc. The narrower the bandwidth, the more easily an antenna design can be optimized.
What is needed in the art is a method of resolving radar returns of a pulse radar system to increase the range resolution without increasing the pulse bandwidth and thus the cost of producing the radar.